OXIDANT-INDUCED CELL DEATH IN RESPIRATORY EPITHELIAL CELLS IS DUE TO DNA DAMAGE AND LOSS OF ATP

Oxidative stress is considered to be an important pathogenic event in ischemia-reperfusion injury, leading to apoptosis or necrosis. We show acute cytotoxicity upon exposure to hydrogen peroxide (H 2 O 2) in BEAS-2B cells and A549 cells. Single-cell gel electrophoresis showed formation of large comet tails from DNA upon oxidant exposure suggestive of DNA damage. The ATP content of the cells decreased upon exposure to H 2 O 2. Preincubation with 3-aminobenzamide (3-ABA), an inhibitor of poly (ADP-ribosyl) polymerase (PARP), prevented the cytotoxicity. The decrease in the ATP content of the cells was also prevented by 3-ABA. Increase in PARP activity was further confirmed by measuring incorporation of [ 32 P]-NAD into nuclear proteins in presence of the cell extracts. Markers of apoptosis were not seen in cells treated with H 2 O 2 with or without 3-ABA pretreatment. These studies suggest that DNA damage is one of the primary reasons for oxidant-induced cell death and that PARP plays an important role in cell death due to its consumption of ATP. Further elaboration of this and other pathways that consume ATP may help prevent oxidant-mediated acute lung injury.